Which is a better leaving group, HO⁻ or H 2 O? Explain your answer.

Hello everyone. Today, we have the following problem which of the following compounds has a better leaving group justify your answer. And so we have a and we have B A is a hydroxyl group attached to an alky group, which is what the R represents. And B is a water that is attached to an alky group. And so a trend is that the more stable the leaving group is after dissociation, the better it is that it can act as a leaving group. And so there's different measures, there are different measures that we can use to assess the ability, the leading group ability. And so we will use charge as this one. And so the charge principles going to state that a leaving group that is neutral after dissociation is more stable than a negatively charged leaving group. So we will essentially draw the dissociation of these two compounds. Such that for example, when aid associates, we will be left with the following, we have a negatively charged species. And of course, we have the ki group and then when bead associates, we have this oxygen molecule which is neutral. And so between these two groups, we can conclude that compound B is more stable and thus a better leaving group. And so with that, we have answered the question overall, I hope it's helped ahead until next time.

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1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

7. Substitution Reactions

Good Leaving Groups

Organic Chemistry

7. Substitution Reactions

Good Leaving Groups

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3:28 minutes

Problem 71

Textbook Question

Which is a better leaving group, HO⁻ or H₂O? Explain your answer.

Verified step by step guidance

Step 1: Understand the concept of a leaving group. A leaving group is an atom or group of atoms that can detach from the parent molecule during a chemical reaction, typically in substitution or elimination reactions. A good leaving group is stable after it leaves, often as a neutral molecule or a weak base.

Step 2: Compare the stability of HO⁻ (hydroxide ion) and H₂O (water) after they leave. HO⁻ is a negatively charged ion, while H₂O is a neutral molecule. Neutral molecules are generally more stable than charged species, making H₂O more stable than HO⁻.

Step 3: Consider the basicity of the leaving groups. HO⁻ is a strong base, meaning it is less stable and more reactive. H₂O, on the other hand, is a weak base and more stable. Weak bases tend to be better leaving groups because they are less likely to react after leaving.

Step 4: Evaluate the role of solvation and stabilization. In a polar solvent, H₂O can be further stabilized due to hydrogen bonding and dipole interactions, whereas HO⁻, being charged, may experience less stabilization compared to the neutral H₂O.

Step 5: Conclude that H₂O is a better leaving group than HO⁻ because it is neutral, more stable, and less basic, making it more favorable for detachment in a chemical reaction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Leaving Groups

Leaving groups are atoms or groups of atoms that can depart from a molecule during a chemical reaction, typically in nucleophilic substitution or elimination reactions. A good leaving group is one that can stabilize the negative charge or is able to exist stably in solution after leaving. The ability of a leaving group to depart is influenced by its bond strength and the stability of the resulting species.

Basicity and Leaving Group Ability

The basicity of a leaving group is inversely related to its ability to leave. Strong bases, like HO⁻ (hydroxide ion), are poor leaving groups because they are unstable and highly reactive in solution. In contrast, weaker bases, such as H₂O (water), are better leaving groups because they can stabilize the negative charge more effectively after departure, making them more favorable in substitution reactions.

Stability of Leaving Groups

The stability of a leaving group after it departs is crucial in determining its effectiveness. Water (H₂O) is a stable molecule that can exist freely in solution, while hydroxide (HO⁻) is a highly reactive ion. The stability of the leaving group influences the reaction's kinetics and thermodynamics, with more stable leaving groups facilitating faster and more favorable reactions.

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